Biology subjects

Kelsoe, G.

Publications and source records attributed to Kelsoe, G..

11 recordsLinked to original sources

bioRxiv2026

Apoptotic Quality Control of Cellular Competence Limits Cryptic Germinal Center B Cell States

Germinal center (GC) B cells undergo extensive apoptosis, but how this process shapes evolving GC populations remains unclear. Using mice lacking intrinsic apoptotic effectors BAK and BAX in B cells, we found that mitochondrial apoptosis was dispensable for affinity maturation but critical for controlling GC size and cellular composition, showing that GC population dynamics and affinity maturation can be uncoupled. BAK/BAX-deficient mice mounted enlarged and prolonged GC responses, largely due to the accumulation of non-proliferating Ki-67loCD71lo dark zone (DZ) B cells. CD71hi and CD71lo DZ cells exhibited similar B-cell receptor (BCR) avidity, retained potential for proliferation and plasmacytic differentiation, and shared clonal lineages, indicating recurrent emergence of non-proliferating DZ populations. A subset also carried Somatic-hypermutation-derived defects that abolished antibody expression despite apparently productive V(D)J sequences; reversion of a single amino acid substitution often restored expression. Mitochondrial apoptosis thus enforces cellular quality control in the GC by limiting the persistence of non-proliferating and expression-defective states while remaining dispensable for affinity maturation.

immunology↗

bioRxiv2026

Asymmetric Boost Responses to an HIV-1 Vaccine: Boost-site Controls Secondary B-cell Fates

Induction of broadly neutralizing antibody (bnAb) responses remains a central challenge to designing efficacious HIV vaccines. Lineage design strategies, in which bnAb precursors are guided via iterative immunizations to their mature forms, depend on high levels of somatic mutation and the recall of antigen-specific B cells. Recent studies have identified spatial context as an important determinant of boosting efficacy, but the application of this to HIV vaccines and the underlying mechanisms are incompletely understood. Here, using mice harboring a V3-glycan bnAb lineage precursor knock-in combined with lineage-tracing and single-cell analyses, we show that persistent germinal centers (GCs) support continued affinity maturation of founder clones and ipsilateral boosting preferentially engages these lineages in secondary GCs. In contrast, contralateral boosting predominantly recruits naive B cells and memory B cells not directed towards the immunizing antigen. The few memory cells recruited at this site were biased towards a plasma cell fate. Finally, we identify disfavored mutational trajectories within the V3-glycan bnAb lineage, revealing intrinsic constraints on bnAb lineage evolution.

immunology↗

bioRxiv2026

Profiling Allogeneic HLA-specific B-cell Responses Utilizing a 64-plex Single-HLA Reporter Cell Panel

Identifying allogeneic HLA-specific B cells in sensitized individuals is essential for defining the cellular basis of allogeneic humoral immunity but remains technically challenging due to their low frequency. To overcome this barrier, we generated a 64-plex single-HLA reporter cell (HLA64-RC) panel that provides a cost-efficient, multiplex, high-throughput platform for screening B-cell specificity. We additionally developed a companion R package, HLA64, for automated data analysis and visualization. Integrated with a streamlined high-throughput BCR discovery workflow, this platform enables reliable identification and characterization of allogeneic HLA-specific B cells from sensitized transplant candidates. In a pilot application, thirteen HLA-specific B cells were identified, enabling linked analyses of phenotype, function, and BCR genetics. These B cells exhibited an IgG+ CD24low phenotype, diverse HLA allele-specificity profiles, and recurrent heavy- and light-chain V-gene usage. In two independent B-cell lineages, clonal members within each lineage displayed divergent binding patterns despite sharing a common clonal origin. Broader application of this approach for systematic profiling of alloreactive B-cell responses will help elucidate the molecular basis of allorecognition, define immunodominant HLA eplets, and ultimately improve immunological risk assessment and allograft outcomes in transplant recipients.

immunology↗

bioRxiv2026

Functional Convergence of Genetically Diverse B-Cell Receptors in Simian-HIV Infected Rhesus Macaques

Germline-targeting or lineage-design vaccine strategies are being used to induce HIV broadly neutralizing antibody (bnAb) responses. These strategies assume that genetically diverse individuals respond similarly to the same immunogen by mobilizing comparable germline precursors, although outcomes vary across bnAb epitopes. Here we explored this premise using a simian-HIV infection model in rhesus macaques. Antigen-unbiased Env- reactive B-cell populations were profiled, followed by systematic analysis of antibody function and B-cell receptor (BCR) genetics. We find that while global Env-reactive B-cell response profiles and antibody functional properties are similar across individuals, underlying BCR genetics are diverse, particularly among non-bnAbs. These results indicate that functional convergence of Env-reactive antibody responses does not necessarily require genetic convergence and suggest that specific germline-targeting may not be an absolute prerequisite for successful vaccine design. These findings support an epitope-focused framework in which bnAb epitopes are engineered to enhance population-level immunogenicity, with potential applicability to other challenging pathogens.

immunology↗

bioRxiv2025

Iterative immunogen optimization to focus elicited responses on a conserved, subdominant influenza hemagglutinin epitope

Designing effective vaccination strategies against genetically diverse viruses, such as HIV or influenza, is hindered by the ability of these pathogens to mutate and readily evade immune responses. While these viruses contain conserved regions that cannot easily mutate without affecting viral fitness, these sites are subdominant, meaning that they are not the primary target of antibodies elicited by natural infection or current vaccines. Here, we integrated recent advances in machine learning methods for protein structure prediction and design to engineer protein immunogens that focus immune responses on a conserved, subdominant HA epitope targeted by broadly cross-reactive influenza antibodies. Iterating between computation-guided optimization and in vivo analyses generated immunogens that faithfully displayed the target epitope and redirected humoral responses toward it upon vaccination. These results provide a blueprint for applying recent protein engineering approaches to immunogen design and may inform the development of broadly protective influenza vaccines.

immunology↗

bioRxiv2023

A broad antibody class engages the influenza virus hemagglutinin head at its stem interface

Influenza infection and vaccination impart strain-specific immunity that protects against neither seasonal antigenic variants nor the next pandemic. However, antibodies directed to conserved sites can confer broad protection. Here we identify and characterize a class of human antibodies that engage a previously undescribed, conserved epitope on the influenza hemagglutinin (HA) protein. Prototype antibody S8V1-157 binds at the normally occluded interface between the HA head and stem. Antibodies to this HA head-stem interface epitope are non-neutralizing in vitro but protect against lethal influenza infection in mice. Antibody isotypes that direct clearance of infected cells enhance this protection. Head-stem interface antibodies bind to most influenza A serotypes and seasonal human variants, and are present at low frequencies in the memory B cell populations of multiple human donors. Vaccines designed to elicit these antibodies might contribute to "universal" influenza immunity.

microbiology↗

bioRxiv2022

An epitope-enriched immunogen increases site targeting in germinal centers

Antibody immunodominance is the asymmetric elicitation of responses against protein antigens. For influenza hemagglutinin (HA), antibody responses often target variable regions on HA and do not provide lasting protection. Next-generation influenza vaccines should elicit antibodies targeting conserved regions such as the receptor binding site (RBS). Understanding how presenting an epitope on a rationally-designed immunogen influences immune responses could help achieve this goal. Here, we compared an engineered RBS-enriched immunogen and its non-enriched counterparts to characterize RBS-directed responses. We found that enriching the RBS-epitope on a single immunogen preferentially expands RBS-directed responses relative to a cocktail of the non-epitope-enriched immunogens. Single B cell analyses showed a genetically diverse RBS-directed population that structural characterization showed engagement of the RBS with canonical features shared with both its receptor and human broadly neutralizing antibodies. These data show how epitope-enriched immunogens can expand responses to a conserved viral site, while maintaining genetic and structural diversity.

immunology↗

bioRxiv2021

Recall of B cell memory depends on relative locations of prime and boost

Re-entry of memory B cells to recall germinal centers (GCs) is essential for updating their B-cell antigen receptors (BCRs). Using single B-cell culture and fate-mapping, we have characterized BCR repertoires in recall GCs following boost immunizations at sites local or distal to the priming. Local boosts with homologous antigen recruit to recall GCs progeny of primary GC B cells more efficiently than do distal boosts. Recall GCs following local boosts contain significantly more B cells with elevated levels of Ig mutations and higher avidity BCRs. This local preference is unaffected by blockade of CD40:CD154 interaction that terminate active, primary GC responses. Local boosts with heterologous antigens elicit secondary GCs with B-cell populations enriched for cross-reactivity to the priming and boosting antigens; in contrast, cross-reactive GC B cells are rare following distal boosts. Our findings indicate the importance of locality in humoral immunity and inform serial vaccination strategies for evolving viruses. One Sentence SummaryThe participation of memory B cells in recall germinal centers depends on whether the boost is local or distal to the priming site.

immunology↗

bioRxiv2020

A prevalent focused human antibody response to the influenza hemagglutinin head interface

Novel animal influenza viruses emerge, initiate pandemics and become endemic seasonal variants that have evolved to escape from prevalent herd immunity. These processes often outpace vaccine-elicited protection. Focusing immune responses on conserved epitopes may impart durable immunity. We describe a focused, protective antibody response, abundant in memory and serum repertoires, to a conserved region at the influenza hemagglutinin head interface. Structures of eleven examples, eight reported here, from seven human donors demonstrate the convergence of responses on a single epitope. The eleven are genetically diverse, with one class having a common, IG{kappa}V1-39, light chain. All of the antibodies bind HAs from multiple serotypes. The lack of apparent genetic restriction and potential for elicitation by more than one serotype may explain their abundance. We define the head interface as a major target of broadly protective antibodies with the potential to influence the outcomes of influenza infection.

immunology↗

bioRxiv2020

Fab-dimerized glycan-reactive antibodies neutralize HIV and are prevalent in humans and rhesus macaques

SummaryThe HIV-1 envelope (Env) is comprised by mass of over 50% glycans. A goal of HIV-1 vaccine development is the induction of Env glycan-reactive broadly neutralizing antibodies (bnAbs). The 2G12 bnAb recognizes an Env glycan cluster using a unique variable heavy (VH) domain-swapped conformation that results in fragment antigen-binding (Fab) dimerization. Here we describe Fab-dimerized glycan (FDG)-reactive antibodies without VH-swapped domains from simian-human immunodeficiency virus (SHIV)-infected macaques that neutralized heterologous HIV-1 isolates. FDG precursors were boosted by vaccination in macaques, and were present in HIV-1-naïve humans with an average estimated frequency of one per 340,000 B cells. These data demonstrate frequent HIV-1 Env glycan-reactive bnAb B cell precursors in macaques and humans and reveal a novel strategy for their induction by vaccination.HighlightsDiscovery of Fab-dimerized HIV-1 glycan-reactive antibodies with a non-domain-swapped architectureFab-dimerized antibodies neutralize heterologous HIV-1 isolates.Antibodies with this architecture can be elicited by vaccination in macaques.Fab-dimerized antibodies are found in HIV-1 naïve humans.Competing Interest StatementThe authors have declared no competing interest.View Full Text

immunology↗

bioRxiv2019

Structure-guided molecular grafting of a complex broadly neutralizing viral epitope

Antigenic variation and viral evolution have thwarted traditional influenza vaccination strategies. The broad protection afforded by a "universal" influenza vaccine will come from immunogens that elicit humoral immune responses targeting conserved epitopes on the viral hemagglutinin (HA), such as the receptor-binding site (RBS). Here, we engineered candidate immunogens that use non-circulating, avian influenza HAs as molecular scaffolds to present the broadly neutralizing RBS epitope from historical, circulating H1 influenzas. These "resurfaced" HAs (rsHAs) remove epitopes potentially targeted by strain-specific responses in immune-experienced individuals. Through structure-guided optimization we improved two antigenically different scaffolds to bind a diverse panel of pan-H1 and H1/H3 cross-reactive bnAbs with high affinity. Subsequent serological analyses from murine prime-boost immunizations show that the rsHAs are both immunogenic and can enrich for RBS-directed antibodies. Our structure-guided, RBS grafting approach provides candidate immunogens for selectively presenting a conserved viral epitope.

immunology↗